1. Field of Invention
The present invention relates to a quick-response reflective display device that has increased display brightness and contrast and that achieves high display quality. The invention also relates to an electronic device having the reflective display device.
2. Description of Related Art
Direct-view display devices can be provided in electronic devices, such as cellular phone and portable information processing devices. Reflective display devices are an example of such devices in which external light, such as sunlight, enters the display device from the viewer side, is reflected inside the display device, and is emitted toward the viewer so as to perform display. A reflective liquid crystal display device is one example of such a reflective display device in which a reflective layer is formed on the surface of one of a pair of substrates, which are placed opposed to each other so as to sandwich a liquid crystal layer, opposite from the light incident side.
In related art reflective liquid crystal display devices, however, since approximately 55% of the light that enters a reflective liquid crystal display device is absorbed by a polarizer disposed on the viewer side of a liquid crystal panel, the display brightness and contrast are lower than those in a transmissive liquid crystal display device that has a backlight therein and performs display with light emitted from the backlight. Moreover, since light transmittance/non-transmittance through the polarizer is controlled by using birefringence of the liquid crystal in the related art reflective liquid crystal display devices, color light, for example, blue light, is emitted toward the viewer when a black display is produced, and thus a pure black display sometimes cannot be produced.
In the liquid crystal display device, display is performed while changing the orientation of liquid crystal molecules in the liquid crystal layer by the application of a voltage to the liquid crystal layer, and therefore the response speed is limited. Accordingly, a digital micromirror device (DMD) has been proposed as a display device that achieves a higher response speed than in the liquid crystal display device (for example, in Japanese Unexamined Patent Application Publications Nos. 5-150173, 5-196881, 5-203888). The digital micromirror device generally includes multiple digital micromirrors disposed on a substrate. A “digital micromirror” refers to a mirror whose angle with respect to the substrate is variable.
The digital micromirror device having such a configuration can perform display by being irradiated with light from a specific direction, can produce a white (bright) display by controlling the angle formed between the digital micromirror and the substrate so that light reflected by the digital micromirror is emitted toward the viewer, and can produce a black (dark) display by controlling the angle between the digital micromirror and the substrate so that light incident on the digital micromirror device does not enter a light-reflecting surface of the digital micromirror, or so that, even when light incident on the digital micromirror device enters the light-reflecting surface of the digital micromirror, after being reflected by the digital micromirror, it is emitted in directions other than the direction toward the viewer. In the digital micromirror device, since the display is thus performed by changing the angle between the digital micromirror and the substrate, a quick response of approximately 103 to 104 times the speed of the liquid crystal display device is possible.
However, when the digital micromirror device is used as a reflective display device, white (bright) display is impossible because the face of the viewer, the background, and the like are reflected in the digital micromirror. Therefore, only a digital micromirror device serving as an optical modulation device to be mounted in a projection display apparatus, such as a projector, exists in the related art, and a digital micromirror device for a direct-view display device does not yet exist in the related art.